High-Performance Organic Semiconducting Polymers by a Resonance-Assisted Hydrogen Bonding Approach

The resonance assisted hydrogen bond (RAHB) is a special type of hydrogen bonding (HB). With the influence of the π-electron delocalization, the RAHB is stronger than normal HB which is solely based on an electrostatic interaction. The carbamate functionalized thiophene-thiazolothiazole-thiophene (CTZ) has been synthesized as a building block for semiconducting polymers. The introduction of the carbamate side chains to thiophene-thiazolothiazole-thiophene (TTZ) provided solubility, enabled RAHB interactions, and enhanced polarity. Single-crystal X-ray diffraction analysis revealed that the RAHB interactions facilitated the coplanarity of CTZ and the close π-contacts between neighboring molecules in the solid state. The CTZ in single crystals adopted a lamellar packing instead of slipped herringbone stacking which was found in single crystals of previously reported TTZs. Two new π-conjugated polymers, PCTZ-T and PCTZ-B, based on CTZ have also been synthesized. The OFET devices based on PCTZ-T showed an average hole mobility of 1.98 cm2 V–1 s–1, threshold voltages of −2.1 to −5.7 V, and ON/OFF current ratios of 106–107. Bulk heterojunction organic photovoltaic devices with PCTZ-B as the donor and Y6 as small molecular nonfullerene acceptors achieved a power conversion efficiency of 12.7%. The results have demonstrated that RAHB is an effective strategy for designing high-performance organic semiconducting polymers.